The invention relates to a wet-running multiple disc brake and more particularly to a multiple disc brake, in particular for a road vehicle, which is wet-running by way of a cooling fluid, and includes stationary stator discs arranged parallel to and spaced apart from one another, between which in each case one rotatable rotor disc is arranged.
Wet-running multiple disc brakes, as are used, for example, in special trucks, and likewise in heavy construction vehicles, tractors and the like, are very low-wear and are operated at a low temperature level. Here, the brake heat which is produced and brake lining wear debris are discharged by way of cooling oil.
The wet-running multiple disc brakes are usually combined with a differential, with the result that the oil of the differential is also used as cooling fluid to operate the multiple disc brake. The oil is guided through a wheel hub and is transported to the outside between the friction faces of the stator discs and the rotor discs as a result of their rotation. This intensive type of cooling makes defined heat dissipation possible via a measurement of the cooling oil flow.
However, this known wet-running multiple disc brake is affected by a series of disadvantages.
In the described special trucks, heavy construction vehicles or heavy tractors, pronounced long-lasting loading of the brakes leads to overheating of the gear oil as a result of the braking heat produced, since the heat can no longer be dissipated completely to the surroundings via the surface of the gear housing. This results in the loss of the lubricating capability of the oil, which can lead to damage of the gear components.
Since the cooling oil is used for lubricating gearwheels, it has a relatively high viscosity because of its function. In the case of clear running, this leads to high drag losses in the air gaps between the rotor discs and the stationary stator discs, and therefore to additional heating of the oil. For this reason, the use of wet-running multiple disc brakes has been limited up to now to slowly running vehicles.
A further serious disadvantage of the known multiple disc brake results from the fact that the braking heat can be guided by the cooling oil flow only via the friction faces, the oil being guided in friction face grooves during the braking operation. The cooling oil flow and, as a result, the possible heat dissipation are therefore limited.
Even after the brake is released, only small throughflow cross sections result on account of very narrow air gaps of from 0.1 to 0.15 mm. For sufficient heat dissipation, it is therefore necessary to keep the energy density therein low by way of a sufficient number of friction contacts.
However, a large number of friction faces and friction discs increases the drag losses of the brake, which, as mentioned, leads to heating of the oil.
Moreover, the overall air play (i.e., clearance gap) is dependent on the number of friction faces and/or friction discs, which results in a large actuation idle travel of the brake in the case of a correspondingly large number. An acceptable actuation idle travel can be achieved only by the fact that the spacing of the friction faces from the rotor and stator discs is kept very small in the non-actuated state of the brake, as a result of which, however, wear and noise problems occur during clear running.
The invention is based on the object of developing a multiple disc brake such that the cooling, that is to say the dissipation of braking heat, is improved substantially.
This and other objects are achieved by a multiple disc brake, in particular for a road vehicle, which is wet-running by way of a cooling fluid, and includes stationary stator discs arranged parallel to and spaced apart from one another, between which in each case one rotatable rotor disc is arranged. In the case of a braking operation, the radially extending stator discs and rotor discs are pressable against one another, with an air gap being overcome, and are separable from one another after the brake is released, with the formation of the air gap. The rotor discs have cooling channels which can be filled with cooling fluid immediately before or at the beginning of the braking operation.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.